Apparatus for making metal powder

ABSTRACT

Apparatus for atomizing molten metal in which the upper portion of a ceramic nozzle distribution element coacts with the bottom of a source of molten metal such as a tundish to form a hollow stream of molten metal An array of fluid nozzles is located within the hollow stream, and the radially outwardly directed fluid jets atomize the falling curtain of molten metal into particulates which are driven outwardly and away from each other by the impinging fluid. The ceramic distribution element is preferably formed with channels which become progressively shallower downwardly toward the bottom of the ceramic element.

United States Patent [191 Lafferty et al. I

APPARATUS FOR MAKING METAL POWDER Inventors: James H. Lafferty; RaymondA.

Reiter; Paul J. Gibilisco, all of Reading, Pa.

Assignee: Carpenter Technology Corporation,

Reading, Pa.

Filed: June 13, 1973 Appl. No.: 369,553

References Cited UNITED STATES PATENTS 12/1919 Earnshaw 266/34 R 11/1966Searight 425/7 June 18, 1974 FOREIGN PATENTS OR APPLICATIONS 1,081,05912/1954 France 425/7 Primary Examiner-Gerald A. Dost Attorney, Agent, orFirm-Edgar N. Jay

[57] ABSTRACT Apparatus for atomizing molten metal in which the upperportion of a ceramic nozzle distribution element coacts with the bottomof a source of molten metal such as a tundish to form a hollow stream ofmolten metal An array of fluid nozzles is located within the hollowstream, and the radially outwardly directed fluid jets atomize' thefalling curtain of molten metal into particulates which are drivenoutwardly and away from each other by the impinging fluid. The ceramicdistribution element is preferably formed with channels which becomeprogressively shallower downwardly toward the bottom of the ceramicelement.

11 Claims, 3 Drawing Figures scope o o o e W BACKGROUND OF THE INVENTIONThis invention relates to new and useful improvements in apparatus foratomizing a stream of molten metal into solidified particulates and,more particularly, to an improved nozzle structure for atomizing thestream of molten metal.

It is, of course, broadly old to atomize or break up a stream of moltenmetal into particulates through the impinging action of high pressurehigh velocity jets. Later refinements include the use of a ceramicnozzle to control the flow of metal from a supplying tundish to theatomizing zone, but even so, such problems as preventing the formationof satellite clusters, preventing backsplatter and metal buildup on themetal transmitting and fluid nozzles and obtaining more efficientconversion of a high percentage of the throughput into usefulparticulates remain.

SUMMARY OF THE INVENTION It is, therefore, a principal object of thisinvention to provide an improved apparatus for atomizing a stream ofmolten metal to form metal powder which minimizes the backsplatter ofmetal and metal buildup on the nozzle itself as well as the formation ofsatellite or particle clusters caused by collisions betweeninsufficiently solidified particles. I

In carrying out the present invention, an atomizing structure isprovided for use with a tundish or other container of a supply of moltenmetal which forms the molten metal into a hollow stream which surroundsan array of outwardly directed fluid nozzles. Jets from the fluidnozzles are directed radially outward from within the hollow metalstream and, on impingement with the stream, atomize it into particulateswhich fall radially outwardly away from each other and from the jetnozzles.

Preferably, the atomizing structure comprises a generally conical orfrustro-conical ceramic element the upper portion of which is insertedinto the bottom of a tundish to cause the flow of molten metal therefromto progress downwardly in a progressively spreading man ner to form athin annular curtain or hollow stream falling from the bottom of theconical ceramic element.

A plurality of outwardly directed fluid nozzles are mounted to form anannular array within the curtain or hollow stream of falling moltenmetal to provide radially outwardly directed fluid jets which impingeagainst and atomize the metal into particulates. To facilitate formationof the desired thin walled curtain or hollow stream of molten metal theceramic nozzle member has a plurality of channels formed on its surfacewhich diverge from each other as they extend downwardly along theconically shaped member. For best results, the depth of each of thechannels becomes progressively less as the circumference of the ceramicmember increases for more uniform distribution of the molten flow.

In another embodiment, instead of discrete fluid nozzles, asubstantially continuousslot is provided from whichan essentiallycontinuous, 360 flow of fluid is emitted for atomizing the metal.

DESCRIPTION OF THE DRAWINGS Further objects and advantages of thepresent invention will be apparent from the following detaileddescription and the accompanying drawings in which FIG. 1 is a somewhatschematic vertical section, partly in elevation, of an atomizingstructure constructed in accordance with this invention;

FIG. 2 is a plan view of the structure in FIG. 1 and the adjacentportion of a tundish in which it is mounted; and

FIG. 3 is a detail vertical section taken along line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will nowbe described in detail in connection with a preferred embodiment thereofas used with an inert gas as the atomizing fluid.

Referring to the drawings in detail, the invention, as illustrated, isembodied in an atomizing structure shown for illustrative purposes inassociation with a tundish generally indicated at S. The structurecomprises a ceramic, frusto-conical distributing element generallyindicated at 6 and a nozzle assembly gener ally indicated at 7 for theatomizing fluid which in this instance is a gas.

The bottom of the tundish 5 is provided with an aperture 8, the sidewall 9 of which is disposed at an angle conforming to the surface 10 ofthe ceramic distributing element 6lso that when the latter is seated inthe aperture 8, the aperture is sealed except for channels 11 fonned inthe ceramic element 6.

The distributing element 6 is supported in operative relation to thetundish 5 on a feed pipe 17, yet to be de scribed, and is preferablyproportioned in such manner that its upper portion projects through andplugs the aperature 8.

The channels 11 formed in the outer surface of the distributing element6 are preferably semicircular in cross section and form an annular arraywith the channels extending downwardly and diverging from one another.Each channel has a progressively smaller crosssection from top to bottomand preferably adjacent to the bottom of the distributing element 6vanish and leave a bottom marginal portion which is free of channels.The channels 11 facilitate the formation of a substantially continuousannular curtain or hollow stream of molten metal which falls from thebottom periphery of the distribution element 11.

The bottom end of the distribution element 6 is recessed to receive andlocate the nozzle assembly 7 on which the former is supported. Thenozzle assembly 7 comprises a top stud or plug 12 and an intermediategenerally tapered portion 13 which together mate with thecomplementarily formed recess in the distributing element 6. Theintermediate portion 13 of the assembly 7 forms a plenum and is providedwith an inclined outer wall 14in which a plurality of fluid nozzles 15are radially disposed. The inclination of wall 14 is such that the axesof fluid nozzles 15, which extend normal to the plane of the wall 14extend in the desired direction for atomizing the molten metal. Theangle of the nozzles is not critical but preferably they converge withthe plane of the surface 10 of the distribution element 6. The lowerportion of the assembly 7 is generally cylindrical and is threaded ontothe gas feed pipe 17.

Thus, the fluid from the nozzles 15 is directed downwardly and outwardlybeneath the outer edge of the bottom of the distributing element 6 forimpingement against and atomization of the molten metal fallingtherefrom in a hollow stream thereby effecting an outward dispersion ofthe atomized particles which thus have more time to solidify beforecolliding with and thus preventing agglomeration with other particles.

While not essential, the walls of the tundish 5 can be heated to ensuredesired fluidity in the molten metal. When required, the tundish 5 canbe inductively heated by providing a susceptor or a separate radiantheating electrode can be provided just below the bottom of the tundish 5and surrounding the atomizing nozzle assembly.

In operation, the pipe 17 is connected to a suitable supply of anatomizing fluid, preferably an inert gas such as argon under a pressurehigh enough to provide the desired atomization of the metal. To that enda pressure of at least about 300 psi is required. Molten metal issupplied to the tundish 5 and covers the upper portion of thedistributing element 6 from which it passes through the channels 11defined by the wall 9 of the tundish bottom aperture and thedistributing element 6. The molten metal spreads out over the lowerportion of element 6 and falls from it in a substantially continuoushollow stream which is broken up and atomized by the jets from nozzles15.

In a further embodiment, most of the nozzles 15 can be merged to providea substantially annular nozzle structure in the form of an annular slotwhich can be continuous except for about three narrow spiders.

While operation of the atomizing structure has been described inconnection with the use of argon, the preferred atomizing fluid, othergases can be used and also a liquid such as water can also be used asthe atomizing fluid.

It is, of course, to be understood that variations in arrangements andproportions of parts may be made within the scope of the appendedclaims. The terms and expressions which have been employed are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed.

What is claimed is:

1. Apparatus for making metal powder by atomizing molten metal for usewith a container for molten metal having a downwardly opening aperture,comprising a distributing element, means for supporting saiddistributing element in said aperture with the lower portion of saiddistributing element extending below said aperture and the upper portionof said distributing element forming an orifice with the wall of saidaperture for the flow of molten metal therethrough, nozzle means belowsaid distributing element and inwardly of the periphery of the latterfor providing atomizing fluid jets outwardly directed with respect tothe axis of said distributing element, whereby fluid exiting from thefluid nozzle means impinges molten metal falling from the periphery ofsaid distributing element to atomize the same and drive the thus formedparticulates outward.

2. The apparatus of claim 1 in which said distributing element has aplurality of downwardly extending channels formed in the surfacethereof.

3. The apparatus of claim 2 in which said channels become progressivelyshallower from the upper to the lower ends thereof.

4. The apparatus of claim 3 in which the lower ends of said channelstemiinate adjacent to and spaced from the bottom peripheral edge of saiddistributing element.

5. The apparatus of claim 4 in which said distributing element isconically shaped, and said channels radiate downwardly.

6. The apparatus of claim 4 in which said distributing element is shapedas a frustum of a cone.

7. The apparatus of claim 1 in which said nozzle means includes aplenum, and said distributing element has a recess formed in the bottomthereof to receive said nozzle means.

8. Apparatus for making metal powder by atomizing molten metal,comprising a container for molten metal and having a downwardly openingaperture, a distributing element, means supporting said distributingelement in said aperture with the lower portion of said distributingelement extending below said aperture and the upper portion of saiddistributing element forming an orifice with the wall of said aperturefor the flow of molten metal therethrough, means forming an array offluid nozzles below said distributing element and inwardly of theperiphery of the latter, said fluid nozzles being outwardly directedwith respect to the axis of said distributing element, whereby fluidexiting from said fluid nozzles impinges molten metal falling from theperiphery of said distributing element to atomize the same and drive thethus formed particulates outward.

9. The apparatus of claim 8 in which said distributing element has aplurality of downwardly extending channels formed in the surfacethereof.

10. The apparatus of claim 9 in which said channels become progressivelyshallower from the upper to the lower ends thereof.

11. The apparatus of claim 10 in which said means forming said fluidnozzles includes a plenum communicating with said fluid nozzles, andsaid distributing element has a recess formed in the bottom thereof toreceive said fluid nozzleand plenum-forming means.

1. Apparatus for making metal powder by atomizing molten metal for usewith a container for molten metal having a downwardly opening aperture,comprising a distributing element, means for supporting saiddistributing element in said aperture with the lower portion of saiddistributing element extending below said aperture and the upper portionof said distributing element forming an orifice with the wall of saidaperture for the flow of molten metal therethrough, nozzle means belowsaid distributing element and inwardly of the periphery of the latterfor providing atomizing fluid jets outwardly directed with respect tothe axis of said distributing element, whereby fluid exiting from thefluid nozzle means impinges molten metal falling from the periphery ofsaid distributing element to atomize the same and drive the thus formedparticulates outward.
 2. The apparatus of claim 1 in which saiddistributing element has a plurality of downwardly extending channelsformed in the surface thereof.
 3. The apparatus of claim 2 in which saidchannels become progressively shallower from the upper to the lower endsthereof.
 4. The apparatus of claim 3 in which the lower ends of saidchannels terminate adjacent to and spaced from the bottom peripheraledge of said distributing element.
 5. The apparatus of claim 4 in whichsaid distributing element is conically shaped, and said channels radiatedownwardly.
 6. The apparatus of claim 4 in which said distributingelement is shaped as a frustum of a cone.
 7. The apparatus of claim 1 inwhich said nozzle means includes a plenum, and said distributing elementhas a recess formed in the bottom thereof to receive said nozzle means.8. Apparatus for making metal powder by atomizing molten metal,comprising a container for molten metal and having a downwardly openingaperture, a distributing element, means supporting said distributingelement in said aperture with the lower portion of said distributingelement extending below said aperture and the upper portion of saiddistributing element forming an orifice with the wall of said aperturefor the flow of molten metal therethrough, means forming an array offluid nozzles below said distributIng element and inwardly of theperiphery of the latter, said fluid nozzles being outwardly directedwith respect to the axis of said distributing element, whereby fluidexiting from said fluid nozzles impinges molten metal falling from theperiphery of said distributing element to atomize the same and drive thethus formed particulates outward.
 9. The apparatus of claim 8 in whichsaid distributing element has a plurality of downwardly extendingchannels formed in the surface thereof.
 10. The apparatus of claim 9 inwhich said channels become progressively shallower from the upper to thelower ends thereof.
 11. The apparatus of claim 10 in which said meansforming said fluid nozzles includes a plenum communicating with saidfluid nozzles, and said distributing element has a recess formed in thebottom thereof to receive said fluid nozzle- and plenum-forming means.